In conventional channel estimation circuits, improvements of the S/N ratio in channel estimation have been often contemplated wherein a threshold is set and noise paths having a level equal to or lower than the threshold are removed (see Japanese Patent Application Laid-open 2000-261412, for example).
FIG. 1 shows an example of construction of a conventional channel estimation circuit.
As shown in FIG. 1, channel estimation circuit 401 of this conventional example includes, tentative channel estimation unit 102, threshold decision unit 404, and effective path detection unit 105.
Tentative channel estimation unit 102 is supplied with received signal Sr and performs channel estimation by making use of a pilot signal contained in received signal Sr and outputs the result of estimation as tentative channel estimation signal Stcest.
Threshold decision unit 404 establishes and outputs threshold signal Sth.
Effective path detection unit 105 is supplied with tentative channel estimation signal Stcest and threshold signal Sth and, after removing noise paths having powers smaller than threshold signal Sth among paths of the tentative channel estimation signal Stcest, outputs the remaining signal as channel estimation signal Scest.
However, the conventional channel estimation circuit shown in FIG. 1 suffers from a problem that the advantage of the removal of noise paths by making use of a threshold cannot be sufficiently obtained in a transmission environment in which noise and interference power levels greatly vary.